Search Publications
The mass of the neutron star in Vela X-1
Kaper, L.; Telting, J. H.; Barziv, O. +2 more
We measured the radial-velocity curve of HD 77581, the B-supergiant companion of the X-ray pulsar Vela X-1, using 183 high-resolution optical spectra obtained in a nine-month campaign. We derive radial-velocity amplitudes for different lines and wavelength regions, and find all are consistent with each other, as well as with values found in previo…
The solar neighbourhood age-metallicity relation - Does it exist?
Holmberg, J.; Feltzing, S.; Hurley, J. R.
We derive stellar ages, from evolutionary tracks, and metallicities, from Strömgren photometry, for a sample of 5828 dwarf and sub-dwarf stars from the Hipparcos Catalogue. This stellar disk sample is used to investigate the age-metallicity diagram in the solar neighbourhood. Such diagrams are often used to derive a so called age-metallicity relat…
The Aromatic Infrared Bands as seen by ISO-SWS: Probing the PAH model
Léger, A.; Moutou, C.; Giard, M. +6 more
We discuss the Aromatic Infrared Band (AIB) profiles observed by ISO-SWS towards a number of bright interstellar regions where dense molecular gas is illuminated by stellar radiation. Our sample spans a broad range of excitation conditions (exciting radiation fields with effective temperature, T_eff, ranging from 23 000 to 45 000 K). The SWS spect…
Measuring cluster temperature profiles with XMM/EPIC
Aghanim, N.; Arnaud, M.; Hughes, J. P. +3 more
Using the PV observation of A1795, we illustrate the capability of XMM-EPIC to measure cluster temperature profiles, a key ingredient for the determination of cluster mass profiles through the equation of hydrostatic equilibrium. We develop a methodology for spatially resolved spectroscopy of extended sources, adapted to XMM background and vignett…
The relationship between star formation rates and mid-infrared emission in galactic disks
Roussel, H.; Sauvage, M.; Vigroux, L. +1 more
The Hα and mid-infrared mean disk surface brightnesses are compared in a sample of nearby spirals observed by ISOCAM. This shows that, in spiral disks, dust emission at 7 and 15 mu m provides a reasonable star formation tracer. The fact that the 15 to 7 mu m flux ratio is nearly constant in various global exciting conditions indicates a common ori…
On the nature of the transition region from the chromosphere to the corona of the Sun
Peter, H.
One of the keys to understand coronal heating is to understand the (magnetic) structure of the atmosphere below the respective coronal features. The EUV emission lines formed in the thin transition region from the chromosphere to the corona present a sensitive tool to study the structure and dynamics of the lowermost corona and its connection to t…
The afterglow of the short/intermediate-duration gamma-ray burst GRB 000301C : A jet at z=2.04
Greiner, J.; Cline, T.; Hurley, K. +23 more
We present Ulysses and NEAR data from the detection of the short or intermediate duration (2 s) gamma-ray burst GRB 000301C (2000 March 1.41 UT). The gamma-ray burst (GRB) was localised by the Inter Planetary Network (IPN) and RXTE to an area of ~50 arcmin2. A fading optical counterpart was subsequently discovered with the Nordic Optica…
Abundant molecular gas in tidal dwarf galaxies: On-going galaxy formation
Duc, P. -A.; Braine, J.; Charmandaris, V. +4 more
We investigate the process of galaxy formation as can be observed in the only currently forming galaxies - the so-called Tidal Dwarf Galaxies, hereafter TDGs - through observations of the molecular gas detected via its CO (Carbon Monoxide) emission. These objects are formed of material torn off of the outer parts of a spiral disk due to tidal forc…
Soft X-ray emission lines from a relativistic accretion disk in MCG -6-30-15 and Mrk 766
Kaastra, J. S.; Sako, M.; Page, M. J. +3 more
XMM-Newton Reflection Grating Spectrometer (RGS) spectra of the Narrow Line Seyfert 1 galaxies
Chromospheric activity, lithium and radial velocities of single late-type stars possible members of young moving groups
Montes, D.; López-Santiago, J.; Fernández-Figueroa, M. J. +1 more
We present here high resolution echelle spectra taken during three observing runs of 14 single late-type stars identified in our previous studies (Montes et al. \cite{M_etal01b}, hereafter Paper I) as possible members of different young stellar kinematic groups (Local Association (20-150 Myr), Ursa Major group (300 Myr), Hyades supercluster (600 M…